For me specifically, Atom was mostly replacing Notepad++. At the time I was testing out Atom, I found that it didn't consistently save the documents you had open during your last session. There may or may not have been other things, that's the biggest one I remember.

Neither it nor Notepad++ could handle gigantic text files, which is a real shame as well, though not a point of comparison.

Switching over from sublime - I noticed the last session problem, found a plugin for that. - Searching for files and ordering of files presented is a bit different; in Sublime I'd get more relevant files first (in a Rails app) typically you're wanting your controllers/models/views first. I haven't spent time comparing but logically I think it should be presenting the files closer to the top of the tree first (well at least in a Rails app), maybe this can be another plugin. - Laziness on my part yet, haven't found the command for vertically selecting all lines at a given position. - Don't open a large minified JS file... kaboom.

Having said that I'm fully stoked with it in other respects; and I can see the minor annoyances getting fixed.